In the above-described SIP telephone set, for accessing a file under the management of a certain call receiving device located in the distance, required is communication by FTP (File Transfer Protocol) or HTTP (Hyper Text Transfer Protocol). In a case, for example, where a session for a voice path is set during telephone conference, it is necessary to establish a session for a data path by FTP or HTTP in order to download a file under the management of a call receiving device other than a session route for the voice path.
In a case where a file exchange application to which voice communication software is newly applied is used, file transmission/reception should be executed through a node equivalent to a proxy server and its transfer rate depends on a capacity of the proxy server. Under these circumstances, demanded is a system which enables file transmission/reception service to be provided without depending on a capacity of a proxy server.
On the other hand, as disclosed, for example, in Patent Literature 1, known is an IP telephone set in which, for enabling reception of text information in line with communication of voice and video, a request for establishing a communication session for the transmission/reception of the text information is generated and the communication session is established based on the request.
Patent Literature 1: Japanese Patent Laying-Open No. 2005-64761.
According to the technique disclosed in the above-described Patent Literature 1, it is possible to realize voice communication and file transmission/reception between a caller and a call receiver by using SIP. For realizing the file transmission/reception service, however, a session for a voice path for voice communication is required and a file transfer rate still depends on a capacity of a proxy server.